In just a matter of years, the CubeSat platform has evolved from a low-cost experimental platform for the academic community into an industry-accepted standard with a robust community of industry, military, and scientific applications. In light of the continuing budgetary pressures for civilian and military space programs, CubeSats, and nanosatellites in general, provide an increasingly appealing and expeditious alternative to traditional spacecraft developments. In addition, the adoption of this platform has resulted in an expanding industry providing commercial off the shelf (COTS) components and subsystems specifically for CubeSat applications, including avionics, attitude determination and control, and power generation and storage. One area that remains under active development is enabling low-cost micro-propulsion systems for CubeSat-scale spacecraft. Without propulsion, CubeSat missions are resigned to a limited scope due to lack of maneuverability and station-keeping capability, and are rarely even considered for missions requiring significant (100s to 1000s of m/s) Delta V. Innovations in electric propulsion are of note but require significant power resources and a mission of sufficient duration to take advantage of low-thrust trajectories.
Presently, the commercial, government, and academic communities are developing systems to meet the needs of mission designers. The commercial aerospace industry has, in the past decade, moved to miniaturize propulsion technology for the CubeSat platform. Advancements are also occurring in the civilian government, military, and academic communities. For example, in 2005-2006, JPL created a multi-functional tank (MFT) for the Micro-Inspector spacecraft. The Micro-Inspector was a 10 kg spacecraft with a vaporizing butane propulsion system. The MFT contained a central butane liquid propellant tank, surrounded by a plenum, into which the butane was allowed to expand and vaporize completely. The low tank pressure (less than 100 psi even in worst temperature cases) allowed for a flat tank geometry except for slightly curved internal tank surfaces to facilitate the desired maximum tank pressure. The flat surfaces provided interfaces for avionics board mounting to provide the heat of vaporization to the butane propellant and in turn allowing for cooling of the avionics. From the plenum tank, eight thrusters were fed to produce attitude control and small delta-v for Micro-Inspector (only 15 m/s).
Despite some advancement in micro-propulsion systems, existing systems still consume a significant amount of the mass, volumetric, and financial resources.